Did one not long ago , started with APC at 10:1 , some bits required more than one hit, depends on how bad it is you may have go to 5:1 , then used tar & glue remover , wiped down then washed. Used turtle wax polish x2 coats and sealed with turtle wax tough coat.
mac

You can use Plain Stardrops @10:1 with warm water......use a mitt Some area are highly polished so be careful what you use, AutoglymSRP from any local store is adequate, do small areas.

You can snowfoam pre-wash just be careful with what you use as a too strong product will not help the window rubber, read the label try a test spot.

A round detail brush with that Stardrops mixtre will get the green mould off, do not use T cut in any form as this with scratch the sealed surface of the paint or aluminum trim, use a dedicated polish.

Once the dirt us loose you can use a PW from a good distance, caravans have insulation that you do not want to be getting wet.

As Chongo mentioned they can be machined polished once clean, just go slowly with the right product.

The one side of our static caravan doesn't get much sun so across the course of year gets green mould on it, BH autofoam in a garden sprayer, soft broom/old washmitt and a hose pipe fetches it all of ours with ease, obviously doesn't give it any bling but nice and clean